Self-referenced electrical method for measuring frequency response of high-speed Mach-Zehnder modulators based on two-tone modulation

摘要

We demonstrated a self-referenced electrical method for measuring frequency response of high-speed Mach-Zehnder modulators (MZMs) based on two-tone modulation. The modulation index and half-wave voltage can be extracted from the heterodyne ratio of two desired components by properly adjusting bias voltage. The method achieves the electrical domain measurement of the frequency-dependent modulation indices and frequency-dependent half-wave voltages of MZMs without any extra calibration for the responsivity fluctuation in the photodetection. Moreover, it reduces half bandwidth requirements of photodetector and electrical spectrum analyzer by carefully choosing a half frequency relationship of two-tone microwave signals. The consistency between our method and the optical spectrum analysis method verifies the simple but accurate measurement.